Esterification methacrolein

Several variations of the above process are practiced. In the Sumitomo-Nippon Shokubai process, the effluent from the first-stage reactor containing methacrolein and methacrylic acid is fed directiy to the second-stage oxidation without isolation or purification (125,126). In this process, overall yields are maximized by optimizing selectivity to methacrolein plus methacrylic acid in the first stage. Conversion of isobutjiene or tert-huty alcohol must be high because no recycling of material is possible. In another variation, Asahi Chemical has reported the oxidative esterification of methacrolein directiy to MMA in 80% yield without isolation of the intermediate MAA (127,128). 

Because of the problems with disposal of the bisulfate waste and the handling of HCN, much research has been devoted to alternative processes. The new processes range from using new feedstocks such as isobutylene / t-butyl alcohol, ethylene, isobutane or methylacetylene to techniques for recycling the HCN and / or ammonium bisulfate279 28°. In 1998 Asahi replaced 60,000 tonnes per year of MMA capacity based on direct oxidation of isobutylene with a new process that also starts with isobutylene. However the new direct oxidative esterification (DOE) process makes MMA by the simultaneous oxidation and esterification of methacrolein, which eliminates the intermediate production of methacrylic acid298. 

Other technologies, already commercially applied or under development, are summarized in Figure 2.63b. Alternative routes of synthesis include (i) ethene hydroformylation to propionaldehyde, which then forms methacrolein by condensation with formaldehyde methacrolein is then oxidized to methacrylic acid (BASF process) (ii) isobuthyraldehyde conversion into isobutyric acid and then oxidative dehydrogenation to methacrylic add (Mitsubishi Kasei/Asahi process) and (iii) oxidation of terf-butyl alcohol to methacrolein followed by oxidation to methacrylic acid and esterification. 

P2 Comments Two-stage catalytic oxidation (isobutylene to methacrolein and then to methacrylic acid final esterification with methanol) complex catalyst system. 

Methyl Methcrylate from Propionaldehyde. Propionaldehyde is produced by the oxo reaction of syngas with ethylene. Reaction of propionaldehyde with formaldehyde and dimethylamine in acetic acid form a Man-nich base salt that can be thermally cracked to methacrolein. Methacrolein can be oxidized to methacrylic acid which is then converted to methyl methacrylate by esterification with methanol. The chemistry is illustrated in Eqs. (31)-(34) ... 

Palladium catalysts are widely used in liquid phase aerobic oxidations, and numerous examples have been employed for large-scale chemical production (Scheme 8.1). Several industrially important examples are the focus ofdedicated chapters in this book Wacker and Wacker-type oxidation of alkenes into aldehydes, ketones, and acetals (Scheme 8.1a Chapters 9 and 11), 1,4-diacetoxylation of 1,3-butadiene (Scheme 8.1b Chapter 10), and oxidative esterification of methacrolein to methyl methacrylate (Scheme 8.1c Chapter 13). In this introductory chapter, we survey a number of other Pd-catalyzed oxidation reactions that have industrial significance, including acetoxylation of ethylene to vinyl acetate (Scheme 8. Id), oxidative carbonylation of alcohols to dialkyl oxalates and carbonates (Scheme 8.1e), and oxidative coupling of dimethyl phthalate to 3,3, 4,4 -tetramethyl biphenylcarboxy-late (Scheme 8.1f). 

Figure 133 Reaction network in oxidative esterification reaction of methacrolein.

Figure 13.5 The biock flow diagram of oxidative esterification process for MMA. (a) TBA oxidation for methacrolein synthesis.

Table 13.1 Catalytic activity for aerobic oxidative esterification of methacrolein (1) with methanol to form methyl methacrylate (2). i...

The oxidative esterification of aldehydes in the presence of alcohols to produce saturated and unsaturated aliphatic esters has been developed at the Nippon Shokubai laboratories a great result is represented by the new synthesis of methylmethacrylate (MMA) from methacrolein, methanol and molecular oxygen, which allows yields up to 50 mol MMA (kg cat)" h" using supported bimetallic gold catalysts under relatively mild conditions (80 °C and 3 MPa) [7]. 

The first example of supported titanium-catalysed DA reaction was reported by Luis et al. in 1992 (Scheme 7.49). In this work, the authors described the preparation of several polymeric alcohols derived from Merrifield resin and their efficiency as ligand in titanium-catalysed cycloaddition between methacrolein and cyclopentadiene with yields between 83-99% and good exo selectivity. With the aim to evaluate the enantioselectivity of the reaction, catalyst 80 was then prepared almost quantitatively by double esterification of tartaric acid with chloromethylated polystyrene and a 1 1 mixture of titanium tetrachloride/titanium tetraisopropoxide. " Despite the good conversion and selectivity toward the exo-cycloadduct, only 3% enantiomeric excess was recorded, which was attributed to the very high reactivity of the system. Recycling of the catalyst was successfully performed by filtration from the reaction media and washing with dichloromethane, and catalyst 80 was reused seven times without significant loss of catalytic activity. 

The technical routes of the commercialized processes of PMMA could be categorized by (i) the direct oxidation process which consists of catalytic oxidation of isobutylene or tert-butanol to methacrylic acid (MAA) in two steps (ii) the methacrylonitrile (MAN) route by ammoxidation of tert-butanol (iii) the BASF s method which employs ethylene, carbon monoxide, and formaldehyde as raw materials (iv) the new ACH process by Mitsubishi Gas Chemical Co. Inc., which does not generate acid waste and (v) the direct oxidative esterification of methacrolein by Asahi Chemical Co. Ltd.[l] For most of the newly developed processes, efforts have been made to minimize the impact of the production on the environment. 

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